Method of lead coating



Jan. 10, 1950 J. MAGNIN 2,493,768

METHOD OF LEAD COATING Filed June 21, 1944. 3 Sheets-Sheet 1 Molten flaxMolten Flux u M w flizforneys Jan. 10, 1950 J, MAGN|N 2,493,768

METHQD 0F LEAD COATING Filed June 21, 1944 3 Sheets-Sheet 2 Jan. 10,1950 Filed June 21, 1944 J. MAGNIN METHOD OF LEAD COATING 3 Sheets-Sheet5 Patented Jan. 10, 1959 METHOD OF LEAD COATING JacqucsMagnin, ChestnutHill, Pa., assignor to Horace C. Knerr Application June 21, 1944,SeriaLNo. 541,318

6 Claims, I inv n ion relates o coatina" me al pa s with. lead. asalubri'cant. to. facilitate successive co1d;workingfoperatibns changing"the shape of the metalwithout. necessity for interme diateiannealingsand/or. pickllngs. Commercially pure d is o dinarily used? The, mainpurposeot the. invention is to :produce a surface whichii's coated withlead and in which the. leadi'adheres even after numerous cold passes,

A .furtti r n mo eis. operform the lead o tings of metals. in, a singleoperation.

A. further. purpose. is to avoid the necessity o pre minars wet bathtreatment bef re actual. leadcoetih andiito use a dry bat tr .ment o ly,

A f er nuro se. ist apply. ac tates o a chlorides or sulphates, ofantimony; bismuth, cadmium or tinrfl'oat'ing. upon th surfac f a moltenba h. oflead. as a means ofprep r ngft surface r iron.anGLOILmetaI-aHQysgen ra s. fo a coeting,.or,ileadifor lubri ating purpos nd to usevarioussaltfi ofir n. f r the sam purpos A. further purpose to apply tanus chl rid stannie chloride. cadmium ch r d or an im ny chlorid fluxeshaving; amni ybo h for n when t. ishe ns. lead" coated a dfo t lead. cotin andithus o facil e h ati operat on and" produce mo e p rmen n n i erresults than could; othe w se b et a d A further purpose is't'ocoatwithlead from a molt n bath of eed ...anc forpu po e br c tion withthe aid of a molten.- fluxfloating on th sur ace Qf'the ead, and. c ngch10- ides; ora e n sulph es f antimony; smuth cadmium or-tin", h ati gpar s'to' be c ated within the molten 'fiux' and'ipassingthem through into e molte e di w e an uncoated surface of the lead-or through thefluxas ay e p e rr d:

A further purpose" in lead'cqating for lubrication is to pass metal'objects to be lead coated through a bath containing zinc chloride andstannicr, or, stannous chloride; cadmium chloride .or' antimony chlorideasan alloying flux, facilicoating with leadupon steel;- copper or brass,chrome-iron and nickel-chrome, for example, reducing the cost oi thecoating; the time and handling required-and the spaceoccupied by theoperation;

A; further pu PQSe is" to unitea lead coating tosteel; iron, copper;brass nickel-chrome; chrome-iron alloys and non-ferrous alloysgenerally-at a: lower--- cost and, in shorter time than previously-havebeen available;

A further purpose is to eliminate the use of mercury compounds indipping operations for coating metals with lead.

A further purpose is to eliminate hydrousbaths other than suchaspickling in preparation: for ultimate dry bath" treatment coatingleadupon various metals.

A further purposeis sul asta-ntially to elimimate the use of ammonium"compounds in a bath for dry treatment of metals tocoatthei'r sur faceswith lead, using a trifling amount only to reduce the formationoifioxid'es' in the bath but permitting the use'cf much more where thisis desired.

A further purpose is to dip-the metals to be coated through the fluxinta t he lead; to move the articles to be coated back and forth withinthe lead and flux and" to advancethe articles along a pathfrom theposition of flux covering to the position of ultimate withdrawal fromthe molten lead, passing them through the flux and bath repeatedly butfinally withdrawing the articles which have been coated bythe lead.

A further purpose is topassthe-articles to be coated through the fluxinto the molten lead, to expose the articles todifferent parts ofthelead bath while shifting them within it and finally to withdraw thearticles through a lead surface free from flux coating.

A further purpose is -to dip the articles by a mechanical dipping devicesuch as a conveyor chain, to heat the device so that' it"will not chillthe lead and to reciprocate theaarticles withinthe molten lead duringtheir progress from a point at which they lie below the flux to a pointat which they are withdrawn from thelead.

Further purposes will appear: in the. specification and in the claims.

Figure 1 is a sectional view of-ratreating pot showing a simpleapplicationofthe? preferred form of my inventions.

Figure 2 is a sectional view: showing a second form of my invention.--Withdrawingz the; metal coated through thBtfllllEi'i'S" objectionableaccording to the salts usedii'n theaflux Itreducesc but does not destroythe lubricantriunction of the lead.

Figure 3 is a vcrtloahsection" showing a form of the invention;corresponding generally with Figure 1 but in? which. a mechan c l ippmechanism is used. The; section is taken upon the line 3-3 of Figure:

Figure 4 is a fragmentarwsectioniot the str uc ture of Figuren'i takeroatright angles-to that of Figure 3.

ing, Serial No. 466,195, filed November 19, 1942,

now abandoned.- Related subject matter to the present-applicationappears in my copending applications Serial No. 541,347, filed June 21,1944, for Metallic lubrication; Serial No. 544,072, filed July 8, 1944,for Method and machine for lead coating; and Serial No. 544,073, filedJuly 8, 1944, now abandoned for Coating method.

In cold working of metals in order tobring them to the required shapeand dimensions the metals usually have to be annealed, pickled andlubricated between each two succeeding cold working operations.

Ductile metals are hardened by cold work, and this is truenotwithstanding diiferences in lubricants.

The degree of hardness produced in the initial stages of cold work issuch that ordinary lubricants are inadequate toovercome the frictionalresistance between the die, etc., and the metal. In suchjcasesreannealing becomes a necessary operation. This ordinarily involvesanother pickling operation to remove the oxides produced by annealing.

Under this invention the coating of lead applied to the surface of the;metal functions as a so much superior lubricant that frictionalresistance is greatly reduced even after many suc- .cessive cold passes.

With various metals initial cold work causes a great increase inhardness over that in the annealed condition but continued cold workdoes not correspondingly increase the hardness.

It has been found that coating certain metals such as iron, steel,copper, brass, chrome-iron, nickel-chrome alloys and non-ferrous alloyswith lead generally acts as a lubricant in drawing tubing, or wiredrawing, deep drawing, stamping, etc. by reason of which after the firstannealing and pickling it is not necessary to repeat these operationsafter a considerable series of mechanical distortions during which thelead coating flows along with the metal but is not eliminated, with theresult that even after as many as six or seven successive reductions ordistortions the metal still shows a lubricating coating of lead.

A coating of lead upon the metal can be produced in various ways.

Another feature of importance is the fact that the lead adheres to .themetal to such an extent that even when in the course of cold drawingoperations the hardness of the metal becomes too great tocarry on thecold work it is still possible to reanneal this metal (provided this isdone in a controlled atmosphere) without destroyingthe lead coating.Therefore with the original lead coating from the start further colddrawing operations can still be performed with the original lead coatingas lubricant. In retort annealing (or controlled atmosphere) the leadcoating is not destroyed and does not form oxides and still retains itslubricating properties.

' Pure lead can be electroplated upon the iron, by electrolytic meansbut the adhesive qualities of this coating are not satisfactory. Thedeposite is pulverulent and crystalline and is rather easily removed. Itisuneconomical as it requires an expensive plant and careful andconstant supervision. It has the one advantage of unsual purity of thelead which is desirable in order that the.

full malleability may be attained; but the lead is not incorporated intothe surface of the metal coated. Full retension of the lead requires ahold of the lead upon the metal similar to that secured by impregnation,by which the lead permeates the surface of the metal.

Another-way in which attempt has been made to incorporate the lead tofasten the lead upon the surface of the metal is by alloying the leadwith a small percent of tin or of antimony. Each of these alloyingmetals hardens the lead to such an extent as, in large measure, todefeat the lubricant effect of the lead upon the surface in subsequentmechanical operations performed upon the metal coated. Coating of metalswith lead alloys has been proposed in a series of patents in which thecoating was planned for protective purposes but in which there seems tohave been no thought of use as a lubricant and in which there is no suchteaching. The character of coating planned was prohibitory for such apurpose inasmuch as the coating bath contained at least two percentoftin and two percent of antimony; Onedisclosure proposes ten percent ofantimony and five percent of tin. In one of the patents a final passageof the coated material through a stannous .chloride flux wascontemplated for the express purpose of giving a thin coating of tin.Though the proportions of the bath were not given the ma.- terial wasconstantly referred to as asolder. It evidently contained a largepercentage of tin.

The purpose of the antimony and tin in these several disclosures wasevidently to use the alloy with tin as a means of making the coatingadhere to the surface of the metal to be'coated.

Another method which has proved to be successful to a certain extent,after annealing and pickling, clips the metal to be coated in an aqueoussolution (i. e. a wet bath) of bichloride of mercury saturated with zincchloride as a preparatory step in the method, and subsequently passesthe metal to be coated through a non-aqueous (dry) molten flux floatingon a molten lead bath. The fiux contains zinc chloride and aconsiderable quantity of ammonium chloride.

The mercury process entails an additional operation and the cost ofbichloride of mercury for the wet step of the process olfsets a greatpart of the savings. v n

One of the difficulties with the bichloride of mercury treatmentis thatthe slightest trace of a. grease before amalgamation preventsamalgamation, and if on the amalgamated surface (for in.- stance fromthe handling of the metal with greasy gloves) prevents the leadfromadhering. Furthermore the bichloride of mercury is a poison and is adangerous chemical with which to deal.

I have discovered that excellent results can be attained by a drydipping process without any preliminary wet process .step such'as, forexample, a bichloride of mercury step. I use a salt derived from a metalwhich has affinity for (i. 'e.

tends to alloy with) both the; lead and the metal which is to be coatedwith the lead. I pickle in the usual Way. r l v The salts preferablyusedarethe chlorides, acetates, borates and sulphates.

Considering the price as well as the desirability, either moltenstannic'or molten stannous chloride floating on the molten lead givesgood results, better than secured from others of the salts named. Eithercadmium or antimony chloride and iron have the same another way ofstating form molten fluxes also gives good results. All three-useseparately or permissibly together-give better results when used withzinc chloride than without it but will operate to lead coat the surfaceof the metal for lubrication purposes if used without zinc chloride. Onthe other hand zinc chloride will not lead coat the surface when usedalone nor when used with ammonium chloride. The sulphates and borates ofbismuth, antimony, cadmium, tin

chloride, will operate without zinc chloride-but better with it-and areimproved by the presence of sodium chloride.

In my dipping operation I dip through a flux which may cover a part onlyof the surface of the lead bath, so that the dipped metal may bewithdrawn from a clear lead surface beyond a partition as in Figure 1;or the metal may be dipped into a completely flux-covered lead bath andwithdrawn through the floating flux of the same bath, as in Figure 2.

In Figure l the tank is shown at with a content of molten lead 6 and apartition I. The flux salts are shown at 8 on the entrance side of thepartition and may comprise various salts in the alternative, includingstannous or stannic chloride or cadmium chloride or antimony chloride,or a borate or sulphate of cadmium, of bismuth, of antimony or of iron.Here again the operation is improved by the use of sodium chloride andof zinc chloride. The clear surface of the bath beyond the partition isshown at 9.

In Figure 2 the pot is shown at 5 holding a molten lead 6 upon which amolten flux 8' floats,

spreading over the entire lead bath. The form of Figure 2 has adisadvantage for lubricating purposes, made worse, of course, where theflux contains tin or any other metal which has a definite hardeningeffect, that where there is a definite layer of the flux left on thesurface of the coating of lead, it reduces the lubricant quality of thecoating of lead.

Because each of the metals, tin, cadmium and antimony, etc. has anafiln'ty for (this may be but will form an alloy with) the metal to becoated and with lead, its salts bywhich the surface of the metal can becovered with lead. This is true of metals generally, that they can belead coated by dipping into a molten bath of commercially pure leadthrough a molten flux if the flux tend to alloy with the metal to becoated, and also with the lead.

The lead coated articles are then withdrawn from the lead bath andallowed to cool when they are ready for such operations as drawing, wiredrawing, rolling or deep stamping without intermediate annealing,pickling and again lubricating.

Because other materials than lead, whether definitely hardening thesurface of the lead or forming an alloy with lead of inferior lubricantquality or not, act as impurities to reduce the effectiveness of thelead as a lubricant, it is quite desirable to have pure lead. It isdifficult, or at least expensive to get chemically pure lead but I havesecured excellent results with a bath of what is known as commerciallypure lead.

The principal benefit of my invention lies in the fact that the union ofthe lead with the outer part of the metal coated includes a permeationof the metal surface by the lead much like impregnation and possiblydesignated as impregnation. It may be a case of alloying with bothmetals.

characteristics as the The chlorides of the different metals used havebeen found to be the most suitable salts and at the same time thecheapest.

Some of the fluxes used successfully by me in lead coating have been asfollows:

' Parts Stannous chloride l Zinc chloride 3 with a small addition fromtime to time of ammonium chloride to reduce oxidation Parts Cadmiumchloride 1 to 2 Zinc chloride 8'to 9 with a smal addition from time totime of ammonium chloride 7 V Parts Ferric chloride 2 Zinc chloride 4Sodium chloride 2 Ammonimum chloride l Ferrous chloride 2 Zinc chloride4 Sodium chloride 2 Ammonium chloride l Iron sulphate (ous) 2 Zincchloride 4 Sodium chloride 2 Ammonium chloride 1 Zinc acetate 2 Zincchloride 4 Sodium chloride 2 Ammonium chloride 1 Zinc borate 2 Zincchloride 4 Sodium chloride 2 Ammonium chloride l Antimony trichloride 2Zinc chloride 4 Sodium chloride 2 Ammonium chloride 1 The reasons backof the action which takes of forming alloy with each of the metals to becoated and the lead, the action being similar to an alloying action butthe flux not entering into actual alloy with either to an extent whichwould deplete it seriously, or whether there be some other reason forthe action. At any rate by whatever flux used the lead coating persiststhrough cold-working with amazing tenacity, so much so that I have beenrequired to remove it after complete cold-working, in order thatgovernment inspectors can make sure of the surface under the lead.

Another measure of the unusual persistence of the lead coating is thefact that in the rare cases of reannealing, during cold working where myinvention has been used, reannealing in a controlled atmosphere (such,for example, as an atmosphere of disassociated anhydrous ammonia) doesnot disturb the lead coating and continued cold working does not requireadditional coating.

I have had great success in cold working of V of the lead which 7 gportsamotor l3.connected by Jnetals which have been coated by my invention,which is -a:-tribut e:to the comparative purity I :have used, andparticularly :tothe fact that-the lead has :been substantially free fromalloying tin-or'alloying other metals :WhiCh would have a hardeningeffect.

I have found that a better vcoatingoi lead is :secured where the metalto be coated, herein referred to generally as the work, is passedthrough the flux and then'is reciprocated or therwise moved back'an'dforward in the flux and lead. In order that the work may engagedifferent parts of the bath and stir the bath, the

work'is'advanced from one range of reciprocation tolanother,progressively :toward the point of withdrawal from the lead. The work iswith- :drawn preferably through a clean lead surface ;:since in thisway, the flux is .not. given opportunity vi to forma final wcoatinguponthe lead. The reciprocation is not suggested in Figure '1 but thewithdrawal throughaclean lead surface Mechanism is not necessary forthefreciproca- 'tionff as "I refer to any movement of the metals ito'becoated, as any such desired mov'ement of "the work articles 'nipulation,dipping the articles into the bath .lin .any suitable container,preferably in the form of 'a cageor-basket, closed to retain the workpieces butpermitting free flow of bath through it. The .basket and workpiece content are moved about in the bath as desired. However, ,aneffective movement can be secured by mechanism. For this reason asuitable machine has been illustrated in Figures v3, 4 and 5 and willnow be described.

A,p1atformBissupported uponlegs and 11, resting upon any suitable base,here shown as the 'upper rim 12 of thepot .5 The platform supbelt M witha pulley I 5. The speed of rotation is reduced through-anysuitablegearbox16 so that the rate of ro- -'tationof-shaft 'l'!willbe low'enough for present purposes. The shaft-carries a crank arm [8connected "by apin 19 with a connecting rod 20. The throw of the crankarm maybe adjusted by connecting the pin I9 with the crank arm atotherpoints, such as at 2|, for example.

A ratchet wheel 22 is mounted upon a shaft 23 supported by bearings uponstruts 24. The shaft carries also spaced sprocket wheels 25 uponwhicheoperate the chains 26 of a chain conveyor 'having conveyor .bars21across from chain to chain constituting flights 28. The bars 21 aremerely supports connected with the chain at convenient pointsbyattachment to tabs 29.

.A partition or division plate 30 suitably sup- ;portedfrom thesidestructure 3| and brackets .32, dips down into the lead bath 6 to preventthe flux 8 from distributing over the surface of the bath. The flux isotherwise confined by box v33. The conveyor bars on their downwardlstrokes pass through the flux into the bath.

.The connecting rod ispivoted to a rocker arm '34 at a distance (rockerarm length or throw) from shaft 23 large enough so that rotation of thecrank arm I 8 will cause oscillation ,only of the arm 34. The arm 34carries a holder .35 for a ratchet plunger 36. The plunger is drawntoward engagement with the teeth of the ratchet wheel by spring 31,capable of being with- A drawn therefrom byhandle38 so-that the ratchetdisc and sprocket wheels can be rotated by hand to any extent desiredwhen the ratchet plunger 36 has been withdrawn from the teeth of theratchet wheel. This makes it possible to turn can be effected by handIna--- .carry the basket The reciprocation seems :to 'have ya scrubbingaction and if the metalto :be coated :be finally taken out-of thesleadata lead surfacetfree from flux there seems to be no film of flux-onthecoating. .Even where 1 out through flux there is little trace of fluxand the metal-coated comes the fluxcan be lselectedtmbe aslittleobjectionable :as possible.

As seen in Figure 4 the preferably'closed work :cages or baskets for.the articles to be coated .are hung .by hooks 1-40 from barsor flights22:1.

The hooks are-connected with thebars orrfiights .111. a positionslightlyto-the right of that shown in Figure '4, after,

which the baskets and the ihooksare :slid to the left so that the 'hooks1001116 beneath guards! I, holding the baskets :in

position upon theflightsa-even when the'baskets are turned upside-:down,astakes'pIace-When the sprocket chains: are-moving upwardly to'ther'left -(Figure.3) of the partition:30.

The lower parts .of the .sprocket achains pass about wheels 42 down inthe ;bath, which-wheels need not besprocket wheels :but maybe pulleys-merely. Bearings 'for the :pulley shaft '43 are supported by stays'extendingldownrfrom the partition :30. It has :notbeen considerednecessary to show thesupportssinzdetail other than to indicate themat45f-in Figure The -pot 5 is conventionally shownas seated in aconcrete bed-dfizhaving-airim 411upon'which the flange '48 of the, potmay 1 be rested. In order that-the metalofthe conveyor,-such as-thechains and the:flights,;may not-chillthe lead bath, a heater issupplied, including .a gas pipe 49 controlled by alves50. Itdischargesgas through a burner nozzle :15 52 maybe fed through an I-so:that hot air at upright pipe-53 and a manifold 54. The manifolddistributes thehot products of combustion -.against the :chain,ipreferably onthe downside of the conveyor, :heating {the "conveyorsufiiciently so that there is no chilling of the molten:lead. The bathmayalso be heated separately'asby an'eleotrical heating unit within'thebath. 'Heater-55-is conventional and is supplied with :current throughwires 56 :protected by'conduitf51.

:individual shown and the drawthe extent Notwithstanding that "there isthat this mechanism will be claimed, ,ing 'is intended to 'beconventional to that it represents .one :mechanism by which :the baskets"for the metal to :be coated may :be moved back and'forward within thelead" bat and across the fluid line. and -it isthedntention to claim themethod as well as the mechanism by which this function is secured. 7 7

Whether the articles-to be coated (work) "be moved by hand orby'mechanism for the purpose, such, for example, asthe'one illustrated,

the present invention oifers considerable advantage in uniformity andcompleteness of coating to be secured by this movement. T V

In operation, :articles .tolbe coated and subsequently to becold-processed :are .placed within the basket and thebasketis-attachedto a'flight .of the conveyor, af.ter which theratchetplunger is withdrawn from -theteeth-of the ratchet wheel while thesprockets and chains are turned to through the flux and into the leadbath and back again so that with reciprocation due ltQ the, mechanismthe basket will re.- .ciprocatehack and forward past the flux :line.

=The'rratchet 'tooth .-is .zreset within :the .ratchet wheel-.atisuchiapointiinithe revolution of-rcrank arm l8 that the reciprocation Willtake place initially premthe desired range in t d pt of the molten poolof lead. The revolution of the crank arm l8 will causeoscillation of thearm 34 with corresponding oscillation of the ratchet wheel and thesprocket wheels, and with successive reversals of limited movements ofthe sprocket chains.

When there has been sufficient reciprocation p t e baske for the ar clei erlr t b tas es; e ratchet p n er wi aws fro the ratchet wheel, thesprocket vchainsare ad- ;vanced-a distance sufficient to .carry thebasket through thelead and out to a part of the bath at whichreciprocation is withn the lead alone the ,articles are withdrawn. The,ratchet plungeris ,allowed to enter a ,diiferentnotch ,in the ratchetwheel. Reciprocation of new basket is begun while other baskets alongthe conveyor are reciprocated where they may be.

While the movement of the basket has been called reciprocation, becauseduring a considerable part of the distance travelled the container willmove in a straight line and back again, as seen in Figure 3, there mayalso be oscillatory movement of the basket where it travels about thecurved portion of the wheel at the bottom of the bath. Adjoining thestraight stretches of the sprocket chains there will be movements whichwill be partially reciprocations and partially oscillations. It is myintention to use reciprocation to cover these various movements.

When there has been sufficient reciprocation of the baskets within themolten bath and flux the ratchet tooth is withdrawn from the ratchetwheel and the sprocket chains are turned to bring the baskets out fromthe bath, the container is drained in a trough 58 or other resting placeand is subsequently cooled.

The coating is followed by cold-process working in dies or by othertools securing the lubricant advantages.

The invention has been quite successful in making cartridge casings froma cupped or fiat blank which is first cupped and then successively drawnto the final size of the casing needed. With the lead coating I haveperformed five successive drawing operations before annealing and then,with a controlled atmosphere I have been able to anneal without losingthe lead coating nor the lubricant quality of the lead coating,continuing to perform other successive drawing operations.

The lead coating forms a basis for continuing cold processing withoutannealing and these operations are contemplated in connection with thecoating.

In view of my invention and disclosure variations and modifications tomeet individual whim or particular need will doubtless become evident toothers skilled in the art, to obtain all or part of the benefits of myinvention without copying the structure shown, and I, therefore, claimall such in so far as they fall within the reasonable spirit and scopeof my claims.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

1. The method of coating a metal cold working blank preparatory to coldworking with at least commercially pure the coating during cold working,which comprises forming a bath of at least commercially pure moltenlead, floating upon the molten lead a flux comprising a metallic saltwhich iszfusible and relatively stable at a temperature. correspondingsubstantially .with that of the molten lead, the salt :being selectedfrom the group consisting of acetates, borates, chlorides and sulphatesof the metals antimony, bismuth, cadmium and tin, passing the metal coldworking blank to be coated repeatedly back and forth across theflux-molten lead interface into the molten lead, and withdrawing themetal cold working blank coated from the molten lead.

' 2. Themethodofrcoating a steel cold working blank preparatory to coldworking .with at least commercially pure lead for lubricating by thecoatingduring' cold working, w hich comprises forming a bath of at:least commercially pure .molten lead, floatin'gupon the molten leada-flux comprising a metallic salt which is fusible and relatively stableata temperature cor-respond.- ing substantially with that of the moltenlead, the salt being selected from the group consisting of acetates,borates, chlorides and sulphates of the metals antimony, bismuth,cadmium and tin, advancing the steel cold Working blank through the fiuxinto the molten lead by a back and forth motion which causes anindividual point on the blank to move repeatedly across the interfacebetween the flux and the molten lead, and withdrawing the steel coldworking blank coated from the molten lead.

3. The method of coating a metal cold working blank preparatory to coldworking with at least commercially pure lead for lubricating by thecoating during cold working, which comprises forming a bath of at leastcommercially pure molten lead, floating upon the molten lead a fluxcomprising a metallic chloride which is fusible and relatively stable ata temperature corresponding substantially with that of the molten lead,the chloride being selected from the group consisting of cadmiumchloride and tin chloride, the flux containing at least 10% of cadmiumchloride or at least 25% of tin chloride, passing the metal cold workingblank to be coated repeatedly back and forth across the flux-molten leadinterface into the molten lead, and withdrawing the metal cold workingblank coated from the molten lead.

4. The method of coating a metal cold working blank preparatory to coldworking with at least commercially pure lead for lubricating by thecoating during cold working, which comprises forming a bath of at leastcommercially pure molten lead, floating upon the molten lead a.

flux comprising a metallic salt which is fusible and relatively stableat a temperature corre--;. sponding substantially with that of themolten lead, the salt being selected from the group consisting ofacetates, borates, chlorides and sulphates of the metals antimony,bismuth, cadmium and tin, and at least one chloride of the classconsisting of zinc, sodium and ammonium chloride, passing the metal coldworking blank to be coated repeatedly back and forth across theflux-molten lead interface into the molten lead, and withdrawing themetal cold working blank coated from the molten lead.

5. The method of coating a metal cold working blank preparatory to coldworking with at least commercially pure lead for lubricating by thecoating during cold working, which comprises lead for lubr t y 76forming a bath of at least commercially pure molten lead, floatingupon'the molten lead a flux comprising a metallic salt which is fusibleand relatively stable at a temperature corresponding substantially withthat of the molten lead, the salt being selected from the groupconsisting of acetates, borates, chlorides and sulphates of the metalsantimony, bismuth, cadmium and tin, and at least two chlorides of theclass consisting of zinc, sodium and ammonium chloride, passing themetal cold working blank to be coated repeatedly back and forth acrossthe flux-molten lead interface into the molten lead, and withdrawing themetal cold working blank coated from the molten lead.

6. The method of coating steel with lead for lubrication purposes forcold working, which comprises forming a bath of at least commerciallypure molten lead, covering the molten lead bath with a molten fluxcomprising a sulphate selected from a group consisting oftin sulphate,cadmium sulphate and antimony sulphate, dippinga wrought steel coldworking blank repeatsteel cold working blank the lead bath at a point 5from flux.

coated with lead from where the bath is free JACQUES L REFERENCES CITEDThe following references are of record in the file of this patent:

UNITED STATES PATENTS Number Date Kalil Dec. 4, 1945

5. THE METHOD OF COATING A METAL COLD WORKING BLANK PREPARATORY TO COLDWORKING WITH AT LEAST COMMERCIALLY PURE LEAD FOR LUBRICATING BY THECOATING DURING COLD WORKING, WHICH COMPRISES FORMING A BATH OF AT LEASTCOMMERCIALLY PURE MOLTEN LEAD, FLOATING UPON THE MOLTEN LEAD A FLUXCOMPRISING A METALLIC SALT WHICH IS FUSIBLE AND RELATIVELY STABLE AT ATEMPERATURE CORRESPONDING SUBSTANTIALLY WITH THAT OF THE MOLTEN LEAD,THE SALT BEING SELECTED FROM THE GROUP CONSISTING OF ACETATES, BORATES,CHLORIDES AND SULPHATES OF THE METALS ANTIMONY, BISMUTH, CADMIUM ANDTIN, AND AT LEAST TWO CHLORIDES OF THE CLASS CONSISTING OF ZINC, SODIUMAND AMMONIUM CHLORIDE, PASSING THE METAL COLD WORKING BLANK TO BE COATEDREPEATEDLY BACK AND FORTH ACROSS THE FLUX-MOLTEN LEAD INTERFACE INTO THEMOLTEN LEAD, AND WITHDRAWING THE METAL COLD WORKING BLANK COATED FROMTHE MOLTEN LEAD.